A,B,C are pipes attached to a cistren.A na d B can fill it in 20 and 30 ..while C empty it in 15 min..If A,B,C open successively for 1 min each.how soon the cistern will be filled?

• 3 hours
  
  3 minutes filling=(1/20)+(1/30)-(1/15)=1/60
  So cistern will be filled in 3/(1/60)=180 minutes or 3 hours
• 8 years agoHelpfull: Yes(1) No(1)
• Answer: 3hours or 180 minutes
  Explanation :
  A fills in 20 min
  A will fill in one minute = 1/20th part
  Similarly,
  B will fill in one minute = 1/30th part
  and c will empty tank in one minute = 1/15th part
  
  son in first three minute part of tank filled = (1/20)+(1/30)-(1/15)
  = 1/60 part
  so 1/60 part in 3 minutes
  total tank will be filled in (3*60) minutes
  = 180 minute or 3 hours
• 8 years agoHelpfull: Yes(1) No(0)